As known, a rapid prototyping (RP) technology is developed from the concepts of forming a pyramid by stacking layers, and the main technical feature is to achieve fast formation. A complicated design can be transformed into a three-dimensional physical model automatically and fast without any cutting tools, molds and fixtures. Thus, the development cycle of new products and research and development cost are largely reduced to ensure the time to market for new products and the first-time-right ratio. Accordingly, a complete and convenient product design tool is provided between technicians and non-technicians (e.g. managers and users), and the product competitiveness and the quick reaction capability of enterprises in the market are improved obviously.
Recently, rapid prototyping technology develops a method for producing three-dimensional physical models by combining jet printing and precise positioning of carriers. The producing method begins by first spreading a layer of powder on the carrier and then printing high viscosity liquid binder on part of the powder by using jet printing technology, so that the liquid binder and the powder stick together to become solidified. After the above steps are repeatedly done, a three-dimensional physical model is produced by stacking multiple layers.
During the processes of spreading powder, printing and taking out the finished product by the conventional rapid prototyping technology, the flying dust usually pollutes the working environment and contaminates the whole three-dimensional object forming apparatus. For maintaining normal operation, a dust-collecting and cleaning task is frequently done after a specified stage of the rapid prototyping technology. In other words, the three-dimensional object forming apparatus using the conventional rapid prototyping technology is labor-intensive. Moreover, the long-term exposure to the flying dust is harmful to the health of the worker.
Nowadays, for improving the cleanliness of the working environment, a powder processing system for a 3D printer is disclosed. FIG. 1 schematically illustrates the architecture of a conventional powder processing system. This powder processing system is disclosed in U.S. Pat. No. 7,971,991, which is filed by Z Corporation on May 26, 2006. As shown in FIG. 1, the conventional powder processing system 1 comprises a construction chamber 10, two overflow chambers 11, 11′, a depowdering chamber 12, a powder container 13, a multi-port valve 14, a hose 15, a powder filter assembly 16 and a dispensing powder container 17.
The excess powder from the construction chamber 10 is collected by the overflow chambers 11 and 11′. After the finished three-dimensional object is cleaned and managed in the depowdering chamber 12, remaining powder is produced. Moreover, new powder is accommodated within the powder container 13. The remaining powder and the new powder are gathered to the multi-port valve 14. Then, by applying a negative pressure, the powder is transmitted to the powder filter assembly 16 through the hose 15. After the powder is filtered by the powder filter assembly 16, the filtered powder is contained in the dispensing powder container 17 so as to be recycled.
Although the conventional powder processing system 1 is capable of recycling the remaining powder or waste powder, there are still some drawbacks. Firstly, by controlling the multi-port valve 14 to switch the airflow path, the powder in the overflow chambers 11, 11′, the depowdering chamber 12 and the powder container 13 can be recycled. As known, the use of the multi-port valve 14 increases the control complexity of the powder processing system 1. Moreover, once the multi-port valve 14 has a malfunction, the powder processing system 1 shuts down. Under this circumstance, the process of recycling the powder cannot be successfully done again. Secondly, for transmitting the powder to the powder filter assembly 16 through the multi-port valve 14 and the hose 15 and filtering the powder to the dispensing powder container 17 through the powder filter assembly 16, the speed of the airflow carrying the powder is very high. In other words, the powder carried by the airflow impacts a filter (not shown) of the powder filter assembly 16 at a high speed. Consequently, the filter of the powder filter assembly 16 is readily damaged, and the use life of the powder filter assembly 16 is shortened. Thirdly, for producing the finished three-dimensional object having better binding strength and more delicate surface, the construction powder for forming the three-dimensional object is a mixture containing a fraction of coarse powder and a fraction of fine powder. However, the conventional powder processing system 1 is only capable of recycling the coarse powder from the overflow chambers 11, 11′ and the depowdering chamber 12 by a single-step filtering procedure. Consequently, the particle size distribution of the remaining powder is not satisfied. For achieving the optimized recycling efficacy, the powder processing system 1 is equipped with the powder container 13 to supply the new powder to the dispensing powder container 17. After the particle size distribution of the remaining powder of the mixed powder is adjusted to the desired value, the construction powder is produced. Since the new powder needs to be additionally provided, the operating cost is increased.
Therefore, there is a need of providing an improved powder recycling system so as to obviate the above drawbacks.